Conventionally, temperature increase control has been known in which sulfur oxides (referring to SO2 or SO3, and will be generically referred to as “SOx” when sulfur oxides are not discriminated hereinafter) are regularly desorbed from the catalyst provided in the exhaust pipe of a diesel engine. JP 2017-106381 A is a literature relating to such temperature increase control, for example. This literature discloses a technique for estimating an SOx amount discharged from the catalyst in the state of SO3 by modeling the reaction of SOx in catalyst. SO3 becomes mist by dissolving in H2O, and it is visually recognized as sulfate white smoke. In the above technique, the target bed temperature of the catalyst is determined so that the amount of SO3 discharged from the catalyst estimated by the model operation does not conflict with the constraint on sulfate white smoke.
Following is a list of patent literatures which the applicant has noticed as related arts of embodiments the present disclosure.
Patent Literature 1: JP2017-106381A
Patent Literature 2: JP2015-169105A